Magnetic valve

ABSTRACT

The present invention discloses a magnetic valve for liquid and gaseous working media, in particular for hydraulic brake systems in automotive vehicles, which includes a first cylindrical housing part that is encompassed on its outside by a magnetic coil and has a cylindrical recess inside which extends in an axial direction to accommodate and guide an axmature, a tappet which is displaceable by the armature in an axial direction in opposition to a resetting spring, a second cylindrical housing part which is arranged coaxially to the first housing part and includes a cylindrical recess extending in an axial direction, the said recess being in connection to outside valve ports and in which a valve seat cooperating with the tappet is arranged. According to the present invention, the first and second housing parts form a housing which is made in one piece of a ferromagnetic material and encompasses the armature over at least part of its longitudinal extension in the shape of a sleeve whose walls are sufficiently thick to reduce the magnetic short-circuit but are not thicker than required to reliably accommodate mechanical stresses.

TECHNICAL FIELD

The present invention relates to a magnetic valve for liquid and gaseousworking media, in particular for hydraulic brake systems in automotivevehicles.

BACKGROUND OF THE INVENTION

WO 94/01708 discloses a magnetic valve of this type. According to theembodiment shown, the said valve comprises a top housing part in theform of a thin-walled sleeve closed on its end and a bottom housing partwith valve seat and passages for the inflow and outflow of a workingmedium. The bottom housing part is sealingly pressed into a valveaccommodation, and the top housing part is encompassed by a magneticcoil. For connecting the two housing parts, a magnetic core is usedwhich is fitted with its bottom cylindrical area into the bottom housingpart and with its top cylindrical area of smaller diameter is fittedinto the top housing part. The transition area has a conical design. Thetop housing part with its conically enlarged bottom end abuts on thetransition area. The magnetic core and the top housing part are fastenedabove the transition area in the bottom housing part by displacement ofplastic material. A tappet is guided in the magnetic core whichcooperates with the valve seat and is connected to a longitudinallyslidable armature that is arranged above the magnetic core in the tophousing part. The armature is urged against the stop formed by the upperend of the top housing part by way of a resetting spring which issupported in the magnetic core and acts in the opening direction of thevalve. When the magnetic coil is energized, a magnetic field developsand causes the armature to urge the tappet against the valve seat inovercoming the resistance of the resetting spring. Thus, the prior artmagnetic valve is illustrated as a normally open valve, called NO valvein short.

The top housing part in this valve is made of a non-ferromagneticmaterial in order to prevent a magnetic short-circuit and permitoperation of the valve with small losses only. This aspect is of specialsignificance when, as is the case in anti-lock systems (ABS) or tractionslip control systems (TCS) in automotive vehicles, there is therequirement of high closing pressures, on the one hand, and smalloverall dimensions, on the other hand. It is a general objective inthese and other cases of application to minimize the magnetic losses tothe greatest possible extent in order to achieve a compromise betweencontrasting requirements which is also reasonable under economicalaspects.

Because the armature must be movable axially for functional reasons, aradial air gap is exactly as necessary as an axial residual air gapbetween the magnetic core and the armature in order to avoid a stickingconnection. Also, the wall thickness of the top housing part which isnot ferromagnetic must be considered as a loss-involving ′air gap′. Morespecifically, the magnetic losses which are produced by the sum of theair gaps in the prior art magnetic valve adopt a value which cannot bereduced any further, not even if highly narrow manufacturing tolerancesare complied with.

The prior art magnetic valve suffers from the additional shortcomingthat its adjustability is very intricate. During the assembly, a thinwasher which corresponds to the residual air gap desired is interposedbetween the armature and the magnetic core. Thereafter, the top housingpart with its contents is inserted into the bottom housing part untilthe magnetic core bears against the bottom housing part in an axialdirection. The tappet which is initially inserted into the armature onlyin a light press fit and is supported on the valve seat is displacedupwardly relative to the armature. Subsequently, the parts aredismantled again, and the tappet is fixed in position in the armature bycaulking.

In the second adjustment step, a washer which corresponds to the desiredair gap in the deenergized condition, hence, which corresponds to theresidual air gap plus working stroke desired is inserted between thearmature and the magnetic core. All parts are assembled again, and thetop housing part is urged into the bottom housing part until themagnetic core bears against the stop. In this arrangement, the armatureis shortened plastically in its top weakened area by the size desired.Thereafter, the assembly must be dismantled and the washer removedbefore the parts can be reassembled and, as described hereinabove,coupled to each other in a third step.

The generic German utility model application No. 8522724.2 discloses amagnetic valve which includes a first cylindrical housing part, made ofa ferromagnetic material, to form the magnetic core, and a secondsleeve-type housing part, made of a ferromagnetic material, toaccommodate a magnetic armature and a valve seat member which has aplurality of pressure fluid ports that are separated hydraulically by atappet fitted to the magnetic armature in the initial position of thevalve. Another housing portion which is made of a non-magnetic materialis provided between the two housing parts. The above-mentioned separatehousing parts are joined in the area of the non-magnetic material.

An object of the present invention is to improve upon a magnetic valveof the type mentioned hereinabove so that the magnetic losses in theworking range of the valve can be reduced further, on the one hand, andthat the valve adjustment can be simplified, on the other hand.

Surprisingly, it has shown that the losses due to magneticshort-circuits are reduced when conventional ferromagnetic automaticsteel is used compared to a magnetic valve of the prior art type whichis comparable in its overall size. This is due to the fact that, on theone hand, at least the losses caused by the radial air gap can bereduced and, on the other hand, magnetic saturation occurs very quicklyin the area of the sleeve due to the small wall thickness. Even atoperating pressures of 200 to 350 bar and in consideration of usualsafety margins, the load-bearing sleeve cross-section can be reduced sothat the short-circuit losses in the one-part housing are lower than inthe prior art two-part housing with a top sleeve-type part made of anon-ferromagnetic material. Besides, material selection and a specificheat treatment offer further possibilities to shift the necessarycompromise in designing the sleeve cross-section so that the magneticshort-circuit losses are further reduced.

Another advantage of the one-part housing design is that it obviates theneed for adapting and joining steps and that it reduces the number ofmanufacturing tolerances to be considered. This becomes apparentespecially in the adjustment of the magnetic valve, wherein due to thelarge number of parts cooperating in magnetic valves for an operatingpressure of e.g. 200 to 220 bar, the operating pressure may vary between200 and 350 bar without adjustment.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical cross-sectional view of a first embodiment of amagnetic valve of the present invention.

FIG. 2 is a view of a second embodiment.

FIG. 3 is a variation of the second embodiment.

FIG. 4 is another variation of the second embodiment.

FIG. 5 is a variation of the first embodiment.

FIG. 6 is a view of a third embodiment.

FIG. 7 is a view of a fourth embodiment.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the embodiment of FIG. 1, the top housing part 1 of the one-parthousing is made of a solid cylindrical portion 6 which is encompassed bya magnetic coil 35, and a downwardly following sleeve 4 which isconnected integrally with the bottom housing part 2 configured as ascrew-type coupling part. The sleeve 4 defines an interior bore 3 a. Thebore 3 a and the top area of the top housing part 1 are used to axiallyguide the armature 3 which is supported, on the one hand, on a resettingspring 21 that acts in the closing direction and an anti-stick washer 22in the solid cylindrical portion and, on the other hand, on the tappet 8which in turn bears against the valve seat 7. The bottom housing part 2has a central bore 5 which is slightly larger than the armature bore 3a, and the step in diameter created by the interface of the two boresprovides an annular housing stop 4 a which can be used as plane ofreference, as will be explained hereinbelow. A tubular support member 6is inserted into the bore 5 which, beside the valve seat 7, includes aninsert 15 and a washer 16 which are used to guide the tappet 8. Theinsert 15 and the washer 16 are both formed in the nature of annularmetal washers, each having axial passages 17 and 18,respectively,extending through their annular bodies. Ideally, in the embodiments ofFIGS. 1-3, the thickness of the insert 15 will be greater than that ofthe washer 16. The insert 15 is pressed into the support member 6 andwelded at its edge, if necessary, and the washer 16 is retained in thesupport member 6 by way of a caulked ring (not referred to). Theinterior of the support member 6 is subdivided by the valve seat 7 intoa top inside space 9 and a bottom inside space 12 which are connected tooutside valve ports 11, 14 by way of a radial respectively axial bore10, 13. Beside the central bore 5 to guide the tappet 8, the insert 15and the washer 16 each have at least one passage 17, 18 for theconveyance of working fluid medium. The tappet 8 is equipped with athrust 19 on which a resetting spring 20 that acts in the openingdirection is supported, and the other thrust of spring 20 is defined bythe washer 16. The thrust 19 is defined by a boss extendingcircumferentially about the tappet 8.

For the stroke adjustment, it is deterimined, on the one hand, how farthe tappet 8 which is preassembled in the support member 6, with theresetting spring 20 compressed and with a support on the valve seat 7,projects from the upper boundary plane of the insert 15, mounted flushwith the support member 6. The upper extremity 6 a of the support member6 will remain in contact with the annular housing stop 4 a at all times.On the other hand, it is determined how far the armature 3 is set backcompared to the plane of reference produced in the housing due to thestep in diameter, with the resetting spring 21 compressed and abutmentof the armature 3 on the top housing part without anti-stick washer. Thethickness of the necessary anti-stick washer 22 is then calculated fromboth measurements.

Reference numerals are used in the following Figures only inasfar asthey are required to explain the differences over the previouslydescribed embodiments. Details which have not been modified or which areper se obvious will not be referred to for the sake of clarity. The sameapplies especially to the illustrated peripheral components, such asseals, end caps and filters, which are customary in magnetic valves ofthis type and well known to the expert in the art.

In the embodiment of FIG. 2, the top housing part 1 has a central bore23 which is expediently stepped and used to accommodate the resettingspring 21 and a cylindrical thrust 24. The bottom housing part 2 withvalve seat 7 and tappet 8 is not modified compared to the FIG. 1embodiment. The armature 3 which, with part of its length, is guided inthe sleeve 4 of the housing 1, 2 is supported on the valve seat 7 by wayof tappet 8 and on the resetting spring 21 by way of an anti-stickwasher 22. Resetting spring 21, in turn, is supported on the ball 25that is sealingly pressed into the bore 23 by way of the thrust 24. Toadjust the desired closing pressure, the ball is pressed in downwardly,when installed into the bore 23, as far as until the bias of theresetting spring 21 on the valve seat 3 produces the desired closingpressure, and the latter pressure is applied from below through thevalve seat either mechanically or hydraulically to the tappet 8. Morespecifically, the ball 25 is slipped in until the valve seat 7, with theapplication of opening pressure, is closed by the tappet 8.

The embodiment according to FIG. 3 differs from the embodiment of FIG. 2in that the ball 25′ in the bore 23′ has only a sealing function ratherthan an adjusting function. The hollow-cylindrical thrust 24′ which isundisplaceably inserted into the housing part 1 serves as a top supportfor the resetting sprng 21, and the bottom support occurs by way of theanti-stick washer 22 on the armature 3′ which includes a central guidepin 28. On the opposite side, the armature 3′ has a plasticallydefonnable bead 29. The housing part 2 again has a stop 30, and bothhousing parts 1, 2 are integrally interconnected by way of a sleeve 4.

To explain the adjustment, the support member 6 with the components itcomprises is once more illustrated in detail in the embodiment of FIG.3a. The tappet 8 bears against the valve seat 7 and is guided by way ofthe insert 15′ and the washer 16′. Washer 16′ is retained in the supportmember 6 by a clamping ring 16 a. In the preassembly, the insert 15′ isslipped into the support member 6 until its top boundary plane 26 isflush with the stop surface 27 of the tappet 8 which abuts the valveseat 7, with the resetting spring 20 compressed. The insert 15′ is fixedin this position in the support member 6. Subsequently, the armature 3′is pushed upwardly until it reaches the stop and the bead 29 is deformedplastically until its stop surface is set back by the desired operatingstroke compared to the stop 30 in the second housing part 2.

The embodiment of FIG. 4 shows a variation of the FIG. 3 embodiment.Only FIG. 4a will be explained more closely. Instead of the insert 15′and the waher 16′, only a washer-type insert 31 with an extended guideportion 32 is provided to guide the tappet 8. The support member 6 isplastically deformable at its top end due to the provision of recessesin the cylindrical edge and the remaining edge portions tapering. It isensured in the preassembly that the top area 33 of the support member 6is urged to retreat by plastical deformation so far that its stop planeis flush with that one of the tappet 8 which then abuts on the valveseat. The further adjustment on the armature 3′ is effected as in FIG.3.

FIG. 5 shows an embodiment wherein exactly as in FIG. 1 the top housingpart 1 is configured as a solid cylindrical area. In contrast to FIG. 1,however, the tappet 8′ is not configured as a component part which ismovable irrespective of the armature 3″ but retained in the armature.This obviates the need for the second resetting spring 20 because thetappet 8′ automatically follows the movements of the armature 3″. Theinsert 15 to guide the tappet 8′ was also omitted. Washer 16′ is stillprovided which is fixed in position in the support member 6′ by acaulking ring (not shown). The plastical deforinability of the top area33 of the support member 6′ was taken from the embodiment of FIG. 4.

For the adjustment, the armature 3″ with the tappet 8′ retained in alight press fit is inserted into the housing and pushed upwardly untilthe stop is reached. Subsequently, the tappet 8′ is pushed upwardlyrelative to the armature 3″ until the stop surface 27′ of the tappet 8′is at a predetermined axial distance from the stop 30 in the housingpart 2. Further, the deformable area 33 is compressed downwardly untilits stop plane is at a defined distance from the valve seat 7.Thereafter, the support member 6 can be slipped into the bottom housingpart 2 until stop 30, with the result that the desired operating strokeis adjusted.

In the embodiment of FIG. 6, the housing 1,2 includes a stopped bore 36whose top portion 37 has the smallest diameter and is closed by aplastically deformable housing wall portion 38 which is designedintegrally with the housing 1,2. A pin 39 is arranged in this portion37. In the mid-portion 40, the axially slidable armature 3″ with theattached tappet 8″ is arranged, as well as a magnetic core 41 with aguide bore for the tappet 8″. A resetting spring 42 which acts in heopening direction is compressed between the armature 3″ and the magneticcore 41. A valve seat 44 is pressed into the bottom portion 43 of thestepped boe 36 which has the largest diameter.

FIG. 6 depicts a variation showing what a customary NO-valve would looklike based on the above suggestions. The position of the sealing ball ofthe tappet 8″ is dictated by the bead 30′ and is adjusted by deformationof the area 38 and the related movement of the pin 39 which haspreviously been pressed in. Tappet 8″ and armature 3″ are rigidlyconnected.

To position the magnetic core 41, the armature 3″ is pressed in so as tobe roughly preposition. The press-in accommodation comprises a coilwhich is thn energized. This causes the air gap to close, and the tappet8″ and said's sealing ball 27′ change their position with respect to thebead 30′. Continued pressing in of the magnetic core 41 causes thearmature 3″ with the tappet 8″ to adopt the optimal position withrespect to the bead 30′.

In the embodiment of FIG. 7, the top portion of the top housing part 1again has a solid cylindrical design. The stepped bore 46 houses thearmature 3″, the anti-stick washer 22, the resetting spring 42′, themagnetic core 41′ and the tappet 8″. A valve seat 44 is pressed into thebottom part 48 of the stepped bore until the stop 30′ is reached.

The tappet 8″ is prepositioned in the armature 3″ only in a light fit inthis case. Both parts are fitted into the housing 1,2, and then thetappet 8″ is displaced upwardly relative to the armature 3″ until thestop surface 27′ of the tappet 8″ again has a predetermined axialdistance from the stop 30′, preferably, until it is flush with the stop30′. Thereupon the magnetic core 41′ is slipped in until its bottom edgeis at the predetermined axial distance from the reference plane definedby the stop 30′ or until the resetting sprin 42′ has a predeterminedbias which can be checked by retraction of the tappet 8″. This permitsadjusting the desired air gap between the armature 3″ and the magneticcore 41′ when the magnetic coil is not energized.

FIG. 7 depicts a variation of FIG. 6 in the positioning of the sealingball 27′ relative to the bead 30′ by displacing the tappet 8″ in thearmature 3″ which is supported on a washer 47. A further considerableincrease in force can be achieved by a washer 22 which is disposed atthe air gap and associated with the magnetic core 41.

The above-mentioned embodiments and possible adjustments permit adaptingthe one-part housing of the present invention to most variousrequirements. More particularly, normally open and normally closedvalves can be achieved, as has been shown. The adding manufacturingtolerances may be adjusted in the assembly in all cases. The manufactureof the housing is less costly than that of multi-part housings. Itnecessitates reduced assembly efforts, and a magnetic valve comprising ahousing of this type is very easily adjustable.

The above-mentioned adjustment possibilities may of course also beused—directly or in a modified form—in other shapes of housings,especially in housings made up of two or more parts, provided similarinstallation conditions prevail. Under certain circumstances, the sameadvantages as in the one-part housing of the present invention may beachieved.

What is claimed is:
 1. A magnetic valve for controlling movements ofliquid and gaseous working fluid contained therein, comprising: a) aunitary housing of a ferromagnetic material, said housing containing twoaxially extending and abutting compound interior bores, the first borehaving a first diameter, the second bore having a second diameter largerthan said first diameter; b) said unitary housing including a firstcylindrical housing part that defines a first cylindrical sleeve, saidfirst sleeve containing said first bore; c) a magnetic coilcircumferentially disposed about said first sleeve, d) an axiallymoveable armature circumferentially supported within said sleeve, andguided therein for reciprocal movement in response to excitation viasaid magnetic coil, e) said housing further comprising a secondcylindrical housing part coaxial with said first cylindrical housingpart; said second housing part defining a second cylindrical sleevecontaining said second bore, wherein the abutting interface of saidfirst and second bores defines an annular stop, wherein said stop facesthe interior of said second bore, and wherein said armature defines aradially disposed end-face which becomes radially aligned with said stopat one reciprocal limit of movement of said armature, f) a tubular valvesupport disposed circumferentially within said second bore and havingone extremity thereof in contact with said stop; g) an annular tappetvalve seat disposed fixedly within and at an opposite extremity of saidtubular valve support from said stop, h) a tappet valve defined by anaxially moveable one-piece, elongated pin body disposed within saidvalve support, said body having a first diameter, and having an annularthrust portion medially of its extremities, said thrust portion defininga boss having radially disposed surfaces, said boss being of a secondand greater diameter than said first diameter of said body; i) anannular washer support member positioned between said thrust portion andsaid valve seat, said support member defining an aperture, said pin bodyextending through, and being radially supported by and moveable withinthe aperture of said washer; and j) a first resetting spring extendingabout one end of said tappet pin body, said spring being supported onand between said annular thrust portion of said pin body and said washersupport member, wherein one end of said one-piece pin body is disposedwithin said tubular valve support for achieving direct physical contactwith the end-face of said armature.
 2. Magnetic valve as claimed inclaim 1, wherein an inside space of the support member is subdivided bythe valve seat, and one part of the inside space is connected to a firstoutside valve port by way of a radial bore and a second part of theinside space is connected to a second outside valve port by way of anaxial bore.
 3. Magnetic valve as claimed in claim 1, wherein a bore forthe tappet includes an insert placed in the top of the support memberand a washer spaced axially with respect thereto, the insert being fixedto the support member in an inside space above the valve seat of thesupport member and aligned with the axis of the tappet, wherein theinsert and the washer each comprise axial passages to convey fluidoperating medium.
 4. Magnetic valve as claimed in claim 3, including asecond resetting spring, wherein the tappet valve pin body in an areabetween the insert and the washer includes a thrust defined by a bossextending circumferentially about said pin body, said thrust providing aradial support surface for one end of said second resetting spring, saidspring providing a force which acts in a direction to open said magneticvalve, wherein said resetting spring is supported at its other end bysaid washer.
 5. Magnetic valve as claimed in claim 4, wherein interposedbetween the armature and the first housing part is said first resettingspring which acts in a direction to close the valve at a force which isin excess of said force of the second resetting spring.
 6. Magneticvalve as claimed in claim 5, wherein interposed between the armature andthe first housing part is an anti-stick washer having a thickness whichis sized for establishing a limit of movement of the armature inresponse to said excitation via said magnetic coil.
 7. Magnetic valve asclaimed in claim 1, wherein said first cylindrical housing part furtherdefines a top housing part at its uppermost extremity, and wherein acentral axial bore is provided in said top housing part, wherein aspherical ball is sized to frictionally engage the top extremity of saidcentral axial bore for sealing said bore against leakage therefrom ofsaid working fluid, a cylinder defining a spacer between said firstresetting spring and said ball, whereby said ball is positioned axiallywithin said central axial bore for contacting and displacing saidcylinder, which contacts said first resetting spring, which contactssaid armature, which contacts said tappet, which contacts said secondresetting spring, in that order, for establishing initial resettingspring adjustments of said valve.
 8. Magnetic valve as claimed in claim3 wherein said armature further comprises a central guide pin comprisinga first integral boss at one end extending axially toward the firsthousing part, and a plastically deformable bead comprising a secondintegral boss at the opposite end, said second boss disposed for directphysical contact with said tappet, said guide pin comprising means forassuring concentricity of said first resetting spring, said deformablebead comprising means for establishing resetting spring adjustments ofsaid valve.
 9. Magnetic valve as claimed in claim 8 wherein the washersupport member further comprises an elongated annular bushing forimparting support to that portion of the pin body of the tappet whichextends between said thrust portion and said valve seat.